The present invention relates to an error performance monitoring system of each call in digital exchange service.
A prior such system is shown in FIG. 2, in which the numeral 1 is a subscriber terminal, 2 is a subscriber-loop terminating equipment, 3 is a transit trunk terminating equipment, 4 is a subscriber-loop path, 5 is a transit trunk path, 6 is a transmission error check information storage, and 7 is an end-to-end transmission error performance evaluation equipment. The communication is carried out between the originating subscriber terminal A (subscriber terminal 1), and the terminating terminal B, through the subscriber-loop paths A and B, the subscriber-loop terminating equipments A and B, the transit trunk terminating equipments A and B, and the transit trunk path 5. A subscriber-loop terminating equipment 2 and a transit trunk terminating equipment 3 measure an error 2b on a path by checking a conventional parity error code. The transmission error check information storage 6 collects error check results, and stores the number of errored blocks in a predetermined duration in each transmission equipment together with the time of error occurrence. The content of the transmission error check information storage 6 is transferred to the end-to-end transmission error performance evaluation equipment 7 in every predetermined period. Then, the evaluation equipment 7 estimates the errored seconds (%ES) of the circuit between the subscriber terminals A and B. The errored second (%ES) is defined as the ratio of the errored seconds to the whole communication time.
However, the prior art of FIG. 2 has the disadvantage in that it is applicable to only a leased circuit, which has fixed paths between subscriber terminals, but it is not applicable to an exchange circuit, in which the combination of the paths between subscribers depends upon each call. Further, in case of ISDN (Integrated Services Digital Network) service, which has different routes or paths between subscribers for each call, it is impossible to measure error performance in a conventional system which has been developed for a leased circuit.